GATE CS 1996 Q2.22 — Combinational Circuits

The given circuit is a standard 4-to-1 multiplexer (MUX) with select lines $A$ (MSB) and $B$ (LSB), and the following input lines:

• $I_0 = C$
• $I_1 = \overline{C}$
• $I_2 = \overline{C}$
• $I_3 = C$

The output equation for a 4-to-1 multiplexer is given by:

Substituting the given inputs into the equation:

This is the sum-of-minterms expansion for the 3-variable XOR operation:

Thus, the circuit implements the 3-input XOR gate, which corresponds to Option C.